The use of clamping mechanisms is widely spread in the cutting tools industry. There are many types of clamping mechanisms for a wide range of uses.
In some cutting tools, a cutting insert, typically made of cemented carbide or other hard material, is retained in an insert holder, typically made of steel. At a large overhang, when the length to diameter ratio of the cutting tool is relatively high, it is advantageous to use a cemented carbide shank in order to increase the overall rigidity of the cutting tool. Such a use of a cemented carbide shank, however, is also advantageous in cutting tools having shorter overhang. With such type of cutting tools, a cutting insert or a plurality of cutting inserts, are retained within an insert holder made of steel, and, the insert holder is retained to a cemented carbide shank.
There are several types of mechanisms for attaching an insert holder to a cemented carbide shank. At some mechanisms, the insert holder is pulled rearwardly by means of a clamping bolt that extends along a through bore in the shank. The clamping of the insert holder to the shank takes place by tightening the clamping bolt from the rear side of the shank. A disadvantage of such a form of clamping is that, in order to replace the insert holder, it is necessary to remove the shank from its position at the tool machine in order to be able to untighten the clamping bolt. Such a task, of course, is labor and time consuming.
In other mechanisms, the tightening of the insert holder is carried out by a clamping bolt that passes through a front side or a peripheral side of the insert holder. The clamping bolt may engage into the insert holder or the shank. Such a clamping requires additional threads to be made, a task that is relatively costly in a cemented carbide shank. Furthermore, additional holes in the insert holder reduce the ability to smoothly remove the chips that are produced during machining.
In other cutting tools, a rear end of the steel insert holder is brazed to a front end of the cemented carbide shank. A disadvantage of such a connection is the relative large distance between the cemented carbide shank and the point of exerting the force on the cutting insert during machining. When the forces exerted on the cutting insert are mainly radial, such a relative large distance reduces the advantage of having a rigid shank, and, enables distortion and vibration to develop in the insert holder.
U.S. Pat. No. 6,394,465 to Guy discloses a clamping device (1, 25, 35) for releasably clamping an insertion member (9, 27, 38) with a shank portion. The clamping device comprising a clamping member having an insertion bore (11, 26, 40) formed by the union of an access bore portion (19A, 31A, 41A) and a gripping bore portion (19B, 31B, 41B) for the free sliding insertion into and withdrawal from the shank portion in respect of the access bore portion and its clamping by a clamping surface of the gripping bore portion on its forced displacement thereinto from the access bore portion. The access and gripping bore portions having longitudinal axes (20A, 20B; 32A, 32B; 43A, 43B) spaced apart at least along a portion thereof.
The clamping device of '465 enables firm clamping of the shank portion by the gripping bore portion. However, the firm clamping is maintained by means of an external force exerted by an additional device such as a sleeve, clamping screw or wrench (17, 29, 35). The external force guarantees that the shank remains pressed against the gripping bore portion. Without the additional device, the clamping device of '465 cannot perform as such, since, any external force applied on the gripped shank, in a direction transverse to a longitudinal direction of the shank, will pull out the shank out of the gripping bore portion.